This new one I got came new with a trojan on it in a pre-intsalled game. Soon as I installed Avast, it found it and got rid of it.. What antivirus do you have?

I am not computer savvy enough to find those buggers on my own and whenever I thought I had one, I just put the recovery CD's in and wiped it clean and started over. Haven't had to do that since I started using Avast and it is FREE!